NUR 300 Lecture Notes - Lecture 6: Ear Canal, Eustachian Tube, Semicircular Canals
23 Oct 2018
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Document Summary
External ear: auricle/pinna: cartilage and skin. Funnels sound waves into the external auditory canal: auditory canal. Cerumen keeps foreign bodies from entering and reaching the tympanic membranes. Middle ear (behind the tympanic membrane: auditory ossicles: malleus incus and stapes, eustachian tube: opening that connects middle ear to nasopharynx and allows passage of air. Usually closed but opens when we swallow or yawn: functions. Conducts sound vibrations from outer ear to central hearing apparatus in inner ear. Protects inner ear by reducing amplitude of loud sounds. Eustachian tube allows equalization of air pressure on each side of tm so that it doesn"t rupture/perforate. Inner ear: bony labyrinth holds sensory organs for equilibrium and hearing. Vestibule and semicircular canals with bony labyrinth compose the vestibular apparatus. Cochlea contains central hearing apparatus: although inner ear isn"t accessible to direct exam, its functions can be assessed.
